The present invention relates to the transmission of information signals between a transmitter and a receiver or between a source and a destination for information signals.
Generally speaking the conduction of voltages, of a current or even of low level signals is in cases provided through electrical conductors which are insulated and end in plug elements having contact plugs and/or sockets which are electrically connected to the conductors. Extension cords and twin conductors of this type are of course conventional for the transmission of electrical power, but the same principle is also being used for other transmission of low level electrical signals such as measuring signals or the like and include the connection between a transducer providing certain measuring functions and a receiver for the measuring signal processing the signal further. A particular field of art is for example the electrical system including a measuring system in an automobile for determining the upper dead center, for controlling an antiblocking system for brakes and other functions to be monitored. To an increasing extent microprocessors are used in automobiles for purposes of monitoring and controlling operating functions and critical data such as firing angle, the launch time of a firing signal, the circuit breaker, the speed of the engine of the vehicle, of an automatic transmission or the like.
The foregoing already indicates that in cases the transmission of signal involves higher frequency signals or signals which run through an environment in which the conduction of the signal may encounter interference. For this purpose it is necessary to completely shield the electrical conductor and of course the equipment at either end may also require complete and adequate shielding. This involves for example also the shielding of the microprocessor because the operating power level of such a processor is quite low so that interfering signals may readily be received unless, as stated, the microprocessor is very securely shielded. Generally speaking, if a system is provided in which so to speak a microprocessor is the central unit and from which a number of conductors run to various measuring points, the likelihood is rather high that any of these conductors operate as an antenna and picks up interfering signals and voltages from the environment. In addition, it has to be considered that in some circumstances and instances the signals themselves are of a high frequency nature so that ordinary conductors are no longer suitable.
It can readily be seen that a system in which a central unit is provided for gathering a plurality of information and measuring data from more or less distant points and which is forced to operate in an environment which is subjected or subjectable to a considerable extent to a high degreee of interference, the entire system must be shielded with no possibility of any leakage point anywhere. This is basically a considerable expense and the mere transmission of measuring signals is thus already an expensive task.
With these and other objects in view, the invention consists of the construction, arrangement, and combination of the various parts of the device serving as an example only of one or more embodiments of the invention, whereby the objects contemplated are attained, as hereinafter disclosed in the specification and drawings, and pointed out in the appended claims.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide for a new and improved transmission of signals between a transmitting end and a receiving end for purposes of operating in an environment which produces electromagnetic interference but the transmission is to be carried out without being encumbered by such interference.
It is another object of the present invention to provide a new and improved transmission cable for signals.
It is a further object of the present invention to provide a new and improved system for remote measuring and transmission of the measuring results by a cable.
It is a still further object of the present invention to provide a new and improved data acquisition system for monitoring a plurality of different conditions, possibly in a highly electromagnetically interfering environment.
In accordance with the preferred embodiment of the present invention, it is suggested to provide, as a basic signal transmission element, a light conductor such as a single conductor or a bundle of light conducting fibers. This light conductor has an entrance end and an exit end. The entrance end is disposed adjacent a light emitting device being electrically connected to a magnetically operating electric pulse generator preferably of the Wiegand type and these two elements as well as the entrance window of the light conductor are sealingly embedded in an electrically insulating and moisture proofing material such that a comparatively thin wall portion is set up adjacent the magnetic field responsive device so that an external magnetic field can operate the generator. This particular end including the sealed in portion is disposed to be responsive to a physically movable condition represented by a locally variable magnetic field. The other end of the light conductor, i.e., the exit window is disposed adjacent a light detector which is connected to an electric circuit preferably including an amplifier and a pulse forming device, and these elements are embedded in a sealed insulating body. Connector elements such as contact pins or sockets are connected to terminals inside this body but are electrically and physically accessible on the outside without endangering the sealing integrity or the embedment. This latter plug type configuration is connected to a microprocessor for purposes of acquisition of the information which is being transmitted through the cable in form of a light signal.
The particular signal transmission system as per the invention therefore has as its salient element a light conducting "cable" and at their respective ends are sealingly embedded light transmitter portions and light receiver portions. A receiver portion converts the optical signal into an electrical signal of suitable level. The light transmitter portion converts a variable magnetic field into an optical signal. This particular transmission system is therefore free from a variety of interferences. First of all the transmitter and receiver sides are physically, i.e. D.C.-conductively decoupled. Moreover, this particular conductor of a signal does not function as an antenna capable of picking up electromagnetic stray fields.
The electrically insulated and insulating and sealing materials and bodies as per the invention are preferably made through molding processes which today can be made in a very simple manner. The light conductor itself should have an insulating cover which usually can readily be made of conventional electrically insulating material. Such cover material in turn provides adequate moisture protection and the cover ends and is sealingly engaged, connected, bonded or even fused to the sealing bodies at the respective ends of the conductor. The insulating layer can be made in an endless fashion, cut to a suitable length, stripped at the ends for purposes of juxtaposing the transmitter and receiver elements whereupon these elements are embedded in the sealing material as the respective bodies are formed, establishing in fact a uniform construction from end to end. The particular device is therefore not only insensitive against electromagnetic interference but is as a whole protected against moisture. In fact the only access, so to speak, is provided at one end where, for example, electrical connector pins emerge from the respective sealing body.
While applicable in principle to a variety of applications and usages, it should be mentioned that the preferred pulse generator to be employed is the so called Wiegand probe. Such a device is described, for example, in German printed patent application 2,143,327. The Wiegand probe consists of a magnetic core made of two different materials around which are coiled wires. A magnetic field which acts upon the particular assembly results in the production of a current pulse which is in fact independent from the speed of the variation of the magnetic field as applied. It is of particular advantage here that the Wiegand probe does note require any operating voltage, but uses the field it detects for generating the power of its output. This is of particular advantage because the Wiegand probe as well as the light emitting diode and possibly additional auxiliary circuit element can be completely enclosed without any feedthrough provision. Further reference to Wiegand probes are found, e.g. in "Wiegand effect pushing . . ", Electronics, Apr. 14, 1977, pp. 39-40; "Wiegand wire . . .", Electronics, July 10, 1975, p. 100 and p. 105; and U.S. Pat. No. 3,602,906.
The particular light transmitter element can be a luminescing diode or a laser diode which elements have a particular threshold so that in a rather simple manner light pulses can be provided. In cases, the output level of the Wiegand probe may be insufficient so that an additional voltage feed into the particular sealed body has to be provided for which of course is also made in a sealed manner. Alternatively, one can use the fact that during operation on output voltage is usually succeeded or preceded or both by voltage output of the probe in opposite direction. This particular situation can be used, for example, to charge a capacitor being likewise embedded at that particular end of the light conductor so that following the reversal of the output voltage of the Wiengand probe as an indication of a particular measuring situation, the capacitor voltage is added to that output voltage of the Wiegand probe and that may well be sufficient to drive the light emitting transmitter.